1. Field of Invention
The invention relates to a conversion apparatus and a controlling method thereof, and in particular, to a power conversion apparatus and a controlling method thereof.
2. Related Art
Recently, due to the rise of the environmental awareness and the gradual depletion of the fossil energy (e.g., petroleum and coal), countries around the world become aware of the importance of the development of the new type energy. The wind power is the inexhaustible energy without the doubt of energy depletion and can also avoid the problem of the energy monopoly. Thus, the countries around the world also actively develop the wind power generation system to expect to reduce the dependence on the fossil energy by increasing the utilization of the wind power.
The wind power generation system needs to convert the electric power, generated from the wind power generator (hereinafter referred to as a wind generator) via an electric power conversion apparatus. In addition to saving or supplying the converted electric power to the load, the converted electric power may also be connected to the power supply grid in parallel. The architectures of the conventional electric power conversion apparatus may be substantially classified into a passive architecture and an active architecture.
In the passive architecture, a passive full-bridge rectifier converts the three-phase power, outputted from the wind generator, into the single-phase power, and then achieves the objects of energy conversion through the operations of an inductor and a switch. Because the use of only a single switch can achieve the energy conversion, the energy loss of the apparatus is extremely small. When being applied to the low wind speed or the low power wind generator, the conversion efficiency of the apparatus is relatively high. However, the passive architecture cannot actively control and adjust the power factor, and the loss thereof also proportionally rises with the increases of the power and the current. When being applied to the middle or high wind speed or the high power wind generator, the power loss of the apparatus upon conversion is relatively high.
In the active architecture, six active switches and three inductors are utilized, and the instantaneous rotating speed is obtained through a rotor position detector (e.g., an encoder) disposed on the generator to control the instantaneous rotating speed, so that the power conversion apparatus can complete the electric power conversion. Because the active architecture can be synchronously changed with the change of the three-phase AC power outputted form the wind generator and can achieve the full power energy conversion, the conversion efficiency thereof is relatively high and the energy loss thereof is relatively low when being applied to the high wind speed or the high power wind generator. However, the active architecture needs to drive six active switches to operate concurrently and needs to supply the power to the position detector disposed on the generator to have the long distance line loss, so that the power loss is much larger than that of the passive system. Thus, the active architecture is not advantageous to the wind energy conversion for the low wind speed or the low power wind generator.
Therefore, it is an important subject to provide a power conversion apparatus, having full power and high efficiency energy conversion and lower power loss, and a controlling method thereof.